Abstract: Base on the correlations of supercritical water reactor,using the degree of similarity,which is included in Fuzzy Mathematics,a new calculation model for calculating the degree of similarity between actual status and the empirical correlations is designed.By this model,the actual status is compared with the empirical correlations,and the best correlation for actual status is obtained.It is indicated that the degree of similarity can be used in the choosing of the best correlations for the problem about heat transfer of supercritical water-cooled reactor,based on the known correlations,resulting in the results with higher accuracy.